Nadine is a very distant cousin of Elmer Boynton. About four years before the events of the story, Lennox had gone out of the house at night, and Mrs Boynton was very angry about it. She then invited Nadine to stay with them. Nadine and Lennox fell in love, got married, and stayed on with the family.
Nadine is described as being young, calm and "dark-haired with a creamy pallor", and a "placid face not unlike a Luini Madonna".
Near the beginning of the novel, Dr Gerard observes that Nadine is the only member of the family who is not afraid of Mrs Boynton. She is unhappy and deeply concerned for her husband, but she is not afraid. He observes that when she glances at her husband, it is a mother's glance, rather than a wife's, because it is protecting and anxious.
Nadine asks Lennox to go away with her, so that they can live lives of their own, and have children, away from the influence of his mother. Lennox does not want to go away, and Nadine says that she will leave, as she feels that she has borne their current life long enough.
Nadine later tells Poirot that she does not feel sorrow over Mrs Boynton's death, but she does feel remorse. She explains that after returning to the camp on the day of the murder, she told Mrs Boynton that she was going to leave Lennox for Mr Cope. She felt that Mrs Boynton had already overexerted herself during the journey to Petra, and the shock and anger of her news was enough to cause her death. She tells Poirot that she never saw Mrs Boynton alive again, and that after that conversation, she went to the marquee and told her husband that she was leaving him.
Nadine also tells Poirot that she owns a hypodermic syringe, but that it was left in their big luggage in Jerusalem.
Nadine tells Poirot that Mrs Boynton was alive and well when she left her, and asks him to accept that she died a natural death. She tells him that Mrs Boynton's death is only just, and that at last there is peace and the possibility of happiness for the family, and asks him to stop his inquiry.
Nadine later talks to Jefferson Cope, and tells him that she cannot leave Lennox for him. He tells her that they will just go back to being old friends.
It is later revealed that Nadine's hypodermic syringe was taken by Raymond Boynton. Nadine tells Poirot that she did not know what had become of it.
It is also revealed that Nadine was lying when she said that she told Lennox that she was leaving him only after speaking to Mrs Boynton. She had told him before returning to the camp.
At the end of the novel, Lennox and Nadine, together with other members of the family, attend a production of Hamlet in which Ginevra is performing. It is revealed that Lennox and Nadine now have children, whom Nadine thinks are old enough to attend the matinee performance.
Appointment with Death (1988 film)
In the 1988 film adaption of Appointment with Death, Nadine is portrayed by Carrie Fisher. The portrayal is fairly faithful to the original with a slight change to how she got involved with the Boynton family. In this adaptation, she was a student nurse and took on a job to look after Mrs Boynton as a way of paying her way through her nursing training. There she met Lennox and married him. Like in the original, Jefferson Cope is also an old flame but her she appears to conduct her affair with Jefferson Cope more actively and openly than in the book. It is not entirely clear whether she did it purely to egg Lennox to stand up for himself or she was actually rekindling her romance with Cope. She does tell Poirot that Qumran was some kind of point of inflexion. She had thought of leaving Lennox for Cope if Mrs Boynton had not died.
Appointment with Death (2008)
In the 2008 ITV adaption of Appointment with Death, Nadine is not featured. It appears that Leonard Boynton, the Lennox Boynton parallel is not married. In any case, he does not live with his stepmother Mrs Boynton. The role of looking after Mrs Boynton's medical needs is taken over by Carol Boynton.